Takumi S, Murai K, Mori N, Nakamura C
Department of Biological and Environmental Science, Faculty of Agriculture, Kobe University, Japan.
Genome. 1999 Dec;42(6):1234-41. doi: 10.1139/g99-077.
To investigate the excision of a maize transposable element in wheat cells, plasmid DNAs containing a Dissociation (Ds) element located between a rice actin 1 gene promoter and a beta-glucuronidase (GUS) gene (gus) were introduced into wheat callus lines by microprojectile bombardment, and transient GUS expression was assayed. The gus-expressing cells after Ds excision were detected only when the Activator (Ac) transposase gene was co-transformed. To further examine a relationship between the amount of Ac mRNA and the Ds excision frequency, the Ds-containing plasmids were introduced into 15 independent transgenic callus lines transformed with the Ac transposase gene. Ten lines expressed the Ac transposase gene under the control of either the cauliflower mosaic virus 35S promoter or the Ac native promoter. The gus gene expression that indicated the Ds excision was observed only in the transgenic callus lines stably expressing the Ac transposase gene. The number of blue spots reflecting the frequency of Ds excision was variable among them. Northern-blot analysis also showed a large variability in the amount of Ac transposase transcripts among the lines. It was however noted that the excision frequency was decreased at a high level of the Ac transposase transcripts, supporting the hypothesis that Ds excision is inhibited above a certain level of the Ac transposase as observed in maize and transgenic tobacco.
为了研究小麦细胞中玉米转座元件的切除情况，通过微粒轰击将含有位于水稻肌动蛋白1基因启动子和β-葡萄糖醛酸酶（GUS）基因（gus）之间的解离（Ds）元件的质粒DNA导入小麦愈伤组织系，并检测瞬时GUS表达。只有当激活子（Ac）转座酶基因共转化时，才能检测到Ds切除后表达gus的细胞。为了进一步研究Ac mRNA量与Ds切除频率之间的关系，将含Ds的质粒导入15个用Ac转座酶基因转化的独立转基因愈伤组织系。10个系在花椰菜花叶病毒35S启动子或Ac天然启动子的控制下表达Ac转座酶基因。仅在稳定表达Ac转座酶基因的转基因愈伤组织系中观察到指示Ds切除的gus基因表达。反映Ds切除频率的蓝点数量在它们之间是可变的。Northern杂交分析还显示各系中Ac转座酶转录本的量有很大差异。然而，值得注意的是，在Ac转座酶转录本水平较高时切除频率降低，这支持了如下假设：正如在玉米和转基因烟草中观察到的那样，Ds切除在Ac转座酶达到一定水平以上时受到抑制。
